1. Field of the Invention
The present invention relates to an endoscope which uses a solid state image pickup element, and more particularly to an endoscope which is capable of displaying the real image that is changing continuously, even during the time when in diagnosis an image is frozen and the frozen image is projected for photographing.
2. Description of the Prior Art
In making an observation and taking a record of the inside of a cavity of a living body, the interior of a mechanical device, or the like, use has been made of an endoscope called a fiberscope in the past.
In recent years, development has been under way for an endoscope that has a miniature solid state image pickup element arranged on the tip, represented by charge coupled device (CCD) and the like.
In an endoscope of the above kind, image fiber that is used in the conventional fiberscope is replaced by a solid state image pickup element that converts the optical image of an object to electrical signals. Ordinarily, the electrical signals are displayed as an image on a display unit such as a CRT monitor via a processing circuit that converts the electrical signals to the television signals. By applying such a new technology to the endoscope, the resolving power (number of the picture elements) that used to be determined in the past by the number (several tens of thousand) of the fibers used will now be determined by the number of the picture elements on the light-receiving surface of CCD. Therefore, it becomes possible now to obtain a resolving power which is about two to three times as high that of the fiber type endoscope. Further, it needs only to insert an electrical signal line to the endoscope probe without requiring several tens of thousand of fibers, so that it becomes possible to reduce the diameter of the probe and has an effect of alleviating the pain to the patient.
Now, some of the endoscopes of the above kind have a freezing function for displaying an image by halting it. Namely, the purpose for having a freezing function which is employed in endoscopic diagnosis for recording an image by taking a photograph or a similar method, is to avoid the blurring in the photographed image which is caused by the movement of the image, if the change in time of the object image on the monitor is wild. For freezing the image, use is made of an image memory, and by an operation at an arbitrary timing of a switch or the like by the technician, instantaneous images are stored in the image memory.
The stored image is projected on the monitor to judge whether or not it is adequate for photographing, and the image is photographed with a Polaroid camera or the like if it is considered adequate.
In the prior-art device, however, for the period of diagnosis during which an image is frozen and the frozen image is photographed by projecting it on the monitor, the continuous presentation of the real image that changes with time is interrupted temporarily. Thus, for instance, in a medical care in which a polyp (disease affected area) is excised by using a pair of forcipes, at the instant of the excision, the operation is ordinarily performed by freezing the image. However, the operation used to be extremely precarious because of the unknown whereabouts of the pair of forcipes at the time of the operation.